# SPDX-License-Identifier: Apache-2.0
# Copyright (C) 2021-2022 OKTET Labs Ltd. All rights reserved.

#
# SQL class for Diary Management Application
#

class SQL_Cache < Hash
    def initialize(sql, table, string_expr)
        @sql = sql
        @name = table
        @string_expr = string_expr
        @lists = Hash.new
        @fields = @sql.query("select column_name from information_schema.columns where table_name='%s'" %
                             @sql.escape(@name)).collect { |col| col["column_name"] }
        super(0)
    end

    attr_reader :sql, :name
    attr_accessor :string_expr

    def search(where)
        list = Array.new
        cmd = "select * from #{@name} where #{where} order by id"
        @sql.query(cmd).collect do |row|
            self[row["id"]] = row.to_h
            list.push(self[row["id"]])
        end
        list
    end
    private :search

    def list(where)
        if not @lists[where]
            @lists[where] = search(where).collect do |entry|
                string = @string_expr.dup
                entry.each do |field, value|
                    string.gsub!(/#\{#{field}\}/, value.to_s) if value
                end
                [entry["id"].to_s, string]
            end
        end
        @lists[where]
    end

    def [](id)
        id = id.to_i
        if super(id) == 0
            if search("id = #{id}").length != 1
                self[id] = nil
            end
        end
        super(id)
    end

    def create(data)
        fields = data.keys & @fields
        cmd =  ("insert into #{@name} (" + fields.join(", ") + ") values (" + fields.collect do "%s" end.join(", ") + ")") %
                (fields.collect do |field|
                  if data[field].class == DateTime
                    t = "STR_TO_DATE('%s'" % data[field] + ", '%Y-%m-%dT%H:%i:%s+00:00')"
                  else
                    t = "'%s'" % @sql.escape(data[field].to_s)
                  end
                  t
                end)
        @sql.query(cmd)
        @sql.query("select last_insert_id() as id").first["id"]
    end

    def modify(id, data)
        fields = (@fields & self[id].keys) - ["id"]
        changes = fields.inject([]) do |ch, field|
            if data.has_key?(field) and data[field] != self[id][field]
                ch.push(field)
            else
                ch
            end
        end
        cmd = ("update #{@name} set " + changes.collect do |field| field + " = %s" end.join(", ") + " where id = #{id}") %
               (changes.collect do |field|
                 if data[field].class == DateTime
                   t = "STR_TO_DATE('%s'" % data[field] + ", '%Y-%m-%dT%H:%i:%s+00:00')"
                 else
                   t = "'%s'" % @sql.escape(data[field].to_s)
                 end
                 t
               end)
        @sql.query(cmd) if changes.length > 0
    end

    def delete(id)
        @sql.query("delete from #{@name} where id = #{id}")
        super(id)
    end
end